This invention relates to a reflecting LED lamp apparatus having a parabolic reflecting surface disposed in a face-to-face relationship with a light-emitting device. The invention also relates to a process for producing the apparatus.
There is known a lamp apparatus for use in optical communication that has a parabolic or concave reflecting surface disposed in a face-to-face relationship with an LED chip that is mounted on a leadframe to face away from the radiation of light such that the reflected light will produce a directional beam. This type of lamp apparatus is described in many patents including Unexamined Published Japanese Utility Model Application (kokai) No. 87567/1989, as well as Unexamined Published Japanese Patent Application (kokai) Nos. 209124/1994, 211940/1995 and 55540/1997.
Unexamined Published Japanese Utility Model Application No.87567/1989 discloses an LED lamp which is generally indicated by B in FIG. 8 and which comprises a metal base 22 having a parabolic concave mirror 21 on a surface that is joined to a light-transmissive resin 26 molded in such a way as to cover a lead plate 24 having an LED chip 23 mounted thereon and a lead plate 25 disposed in proximity to the lead frame 24.
Unexamined Published Japanese Patent Application No.209124/1994 discloses a photoelectronic apparatus that has a reflector mirror combined with a leadframe having a semiconductor chip mounted thereon and that has all components but the leg portions of the leadframe encapsulated with a light-transmissive resin to form a monolithic unit.
Unexamined Published Japanese Patent Application No. 211940/1995 discloses an LED apparatus that comprises a frame member made of an opaque resin having a recess formed in a reflecting surface and a leadframe with an LED chip that is mounted on a frame member, with all components being encapsulated with a transparent or semitransparent resin.
Unexamined Published Japanese Patent Application No. 55540/1997 discloses a light emitter that comprises a pedestal with a concave surface to be mounted on a substrate and a light-emitting diode device that is joined to said pedestal and which comprises a light-emitting element, lead terminals and a light-transmissive resin package that encapsulates said light-emitting element and lead terminals and which has a convex surface that fits said concave surface.
These prior art apparatus, however, have various problems. In the LED lamp B shown in FIG. 8 according to Unexamined Published Japanese Utility Model Application No. 87567/1989, the high heat from the reflow soldering as applied for surface mounting on a substrate passes through the metal base 22 to be directly transmitted to the interface between the concave mirror 21 and the light-transmissive resin package 26 so that cracking or peeling may potentially occur at the interface on account of the thermal expansion mismatch and this introduces difficulty in achieving surface mounting by reflow soldering. In addition, the parabolic surface of the concave mirror 21 is formed by polishing which is a time-consuming operation. As a further problem, in order to ensure electrical insulation between the concave mirror 21 and the lead plate 25, the latter must be made xe2x80x9cfloatingxe2x80x9d from the associated mounting groove on the surface of the metal base 22 but then a spacer 27 to prevent leakage of light from the groove must be interposed by a complex fitting procedure.
In the invention described in Unexamined Published Japanese Patent Application No. 209124/1994, the reflector mirror is mounted on the leadframe by means of various engaging elements and this increases the complexity of the operations for working and assembling the engaged portions; as a result, the temperature variations that occur when the lamp is turned on and off impose a significant load on the engaged portions to eventually shorten the operating life of the LED. In addition, as the lamp size decreases, the size of the engaging elements will unavoidably become smaller, making it more difficult to perform the working and assembling operations. What is more, the small engaged portions result in a weaker joining force, which may potentially produce an instable joint. If resin sealing is attempted in spite of the instable joint, the resin will get into any gap present in the joined area and the reflector mirror is offset from the correct position to eventually cause a serious adverse effect on the optical characteristics of the lamp. Further in addition, if the reflector mirror is to be formed of an insulator such as a plastic material with a thin reflective metal film, a cumbersome evaporating or sputtering procedure must be performed to give a uniform thickness of metal film but then a vacuum drawing apparatus and other large-scale and expensive, dedicated equipment become necessary.
In the invention described in Unexamined Published Japanese Patent Application No. 211940/1995, the reflective surface is formed of an opaque resin and hence has a problem with surface gloss compared to the metallic reflecting surface. In addition, the leadframe is simply placed on the frame member to have contact with grooves cut in the area surrounding the reflecting surface but this presents problems not only with electrical insulation but also the leakage of light from the groove.
In the invention described in Unexamined Published Patent Application No. 55540/1997, the pedestal is made of a resin and its concave surface is typically coated with an evaporated film of a reflective metal such as aluminum, with the evaporated film in turn being protected with a resin overcoat. Because of this layer arrangement, the light emitter requires a complicated process to fabricate. In addition, the interface between the reflector mirror and the light-emitting diode device might undergo peeling or delamination due to aging from the moisture in the surrounding atmosphere and other factors.
To summarize, the prior art lamp apparatus for use in optical communication have had the following problems.
(1) Generally speaking, the manufacturing process consists of so many steps that it is not highly efficient in mass production, and it requires dedicated, large-scale equipment for creating a reflective surface, thus increasing the cost of the product.
(2) In a particular case where the metal reflecting surface is coupled to lead terminals by joining or by means of engaging elements, the temperature variations that occur when the lamp is turned on and off will impose a significant load on the coupled area, thereby causing adverse effects on the operating life of the LED lamp.
(3) Further, in order to produce an apparatus of the type that requires the formation of a thin metallic reflective surface by evaporation or sputtering, dedicated large-scale equipment such as a vacuum drawing apparatus must be employed to reduce the unevenness in the thickness of the reflector and this has limited the effort to reduce the initial cost.
(4) When the thin metallic reflective surface is exposed to high temperatures from reflow soldering during surface mounting of the lamp apparatus on a substrate, it may fail to withstand the thermal expansion mismatch with the contacting resin material, whereupon cracking or delamination occurs to cause its deterioration.
(5) If the reflecting surface is provided with a resin coat, air atmosphere or moisture may permeate into the interface, thereby causing time-dependent deterioration due to the peeling of the reflector.
The present invention has been accomplished under these circumstances and has as an object providing a reflecting LED lamp apparatus of a type that has a concave reflecting surface formed in a face-to-face relationship with an LED chip, which is improved in that it can be produced by a significantly simplified, hence highly productive, commercial manufacturing process, is rigid, has high heat resistance as exemplified by insensitivity to the heat applied during surface mounting, will not undergo time-dependent deterioration and is available at low cost.
Another object of the present invention is to provide a process for producing such an improved LED lamp apparatus.
In order to attain its first object, the present invention provides a lamp apparatus for use in optical communication that comprises leadframes having an LED chip mounted on a lead terminal and a material having a concave reflector mirror opposed to said LED chip and which is resin molded monolithically with said leadframes, said lamp apparatus being produced by a process comprising the steps of making a unitary assembly of a metallic leadframe stock with frame portions on which leadframes are supported by means of support bridges and a concave reflector mirror stock with frame portions on which a concave reflector mirror is supported by means of support bridges, said unitary assembly being formed by joining the frame portions of the leadframe stock to those of the concave reflector mirror stock, completely burying said LED chip, said lead terminal and said concave reflector mirror within a light-transmissive resin by molding, and cutting off the support bridges of said leadframe and those of said concave reflector mirror so that the frame portions of the respective components are severed.
In an embodiment, said leadframe stock with frame portions is obtained from a metal sheet by blanking or etching.
In another embodiment, said concave reflector mirror stock with frame portions is obtained by first blanking or etching a metal sheet and then press forming it.
In yet another embodiment, said lead terminal is bent such that it straddles the peripheral edge of said concave reflector mirror without contacting it.
In still another embodiment, said leadframe stock with frame portions and said concave reflector mirror stock with frame portions are obtained from metallic sheets of the same material and thickness.
In further embodiment, the central area of the underside of said light-transmissive resin in which said lead terminal and said concave reflector mirror are buried is shaped to protrude downwardly, those portions of a pair of said leadframes which are exposed to the outside of said light-transmissive resin are bent downward along the outer lateral sides of said light-transmissive resin whereas the end portions of said leadframes are bent back to become level with the underside of said light-transmissive resin, thereby forming apparatus supporting surfaces.
To attain its second object, the present invention provides a process for producing a lamp apparatus for use in optical communication that comprises leadframes having an LED chip mounted on a lead terminal and a material having a concave reflector mirror opposed to said LED chip and which is resin molded monolithically with said leadframes, said process comprising the steps of blanking or etching a metal sheet to make a leadframe stock with frame portions on which leadframes are supported by means of support bridges, blanking or etching a metal sheet and press forming it to make a concave reflector mirror stock with frame portions on which a concave reflector mirror is supported by means of support bridges, forming a unitary assembly of said leadframes and said concave reflector mirror by joining their respective frame portions, completely burying said LED chip, said lead terminal and said concave reflector mirror within a light-transmissive resin by molding them with the resin, and cutting off the support bridges of said leadframes and those of said concave reflector mirror so that the frame portions of the respective components are severed.
In an embodiment, a plurality of said leadframe stocks with frame portions are formed in a single metal sheet and a corresponding number of said concave reflector mirror stocks with frame portions are formed in a single metal sheet and said leadframe stocks are joined to the corresponding concave reflector mirror stocks, molded with a resin altogether and followed by resin molding of the entire assembly and severing of the respective frame portions so as to produce a plurality of lamp apparatus simultaneously.
In another embodiment of its first aspect, the present invention provides a lamp apparatus for use in optical communication that allows for spatial transmission of sound and image data from a video camera to a television monitor equipped with a light-receiving device.
In yet another embodiment of its first aspect, the present invention provides a lamp apparatus for use in optical communication that allows for spatial transmission of image data from a digital camera to a computer equipped with a light-receiving device.
In still another embodiment of its first aspect, the present invention provides a lamp apparatus for use in optical communication that allows for the distance between successively running automobiles to be measured from above a traffic signal.
In a further embodiment of its first aspect, the present invention provides a lamp apparatus for use in optical communication that allows for the detection of an object approaching a restricted area.
In a still further embodiment of its first aspect, the present invention provides a lamp apparatus for use in optical communication that allows for remote control of a consumer electric or electronic appliance equipped with a light-receiving device.
In yet another embodiment of its first aspect, the present invention provides a lamp apparatus for use in optical communication that allows for spatial transmission of light in a local area network (LAN).